Semi-automatic telephone system.



APPLIGATION ILEE'APEIBO, 1 907.

Patented N0v.8, 1910.

8 SHEETS-SHEET 1.

0. R. AUSTIN. SEMI-AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED APR. 30,1907.

Patented Nov. 8, 1910.

'0. R. AUSTIN. SEMI-AUTOMATIC} TELEPHONE SYSTEM.

APPLICATION FILED APR.30,1907.

Patented Nov. 8, 1910 3 SHEETS-SHEET 3.

, fiwenior (ZarZes m m burr STATES PATENT orFIoE.

' CHARLES R. AUSTIN, OF

LONGBEACH, CALIFORNIA.

SEMI-AUTOMATIC TELEPHONE SYSTEM.

' Specification of Letters Patent.

Patented Nov. 8, 1910.

Application and April 30, 1507. Serial r... 371,188.

To all whom it may concern:

Be it known that I, CHARLES R. AUSTIN,

a citizen of the United States, residing at tem wherein a central station is connected by trunk lines to a plurality of sub central stations serving'different parts of the district,

the subscribers lines being grouped or ra-' diating from the subcentral station.

The main object .of the present invention is to provide for the supervision and control.

which is only obtainable by manual operation at the central station, and at the same time to eliminate expense of an operator at the sub central stations. By providing an automatic sub central station it is possible to provide a number of subcentral stations to serve a given district with but little expense. Where an operator is required at a sub central station it is necessary to make the same serve a considerable district to pay the BX- pense of the operator, but with an automatic sub central station the sub central station district may be made comparatively small and the service wires to the sub-' scribers proportionately short, thereby greatly reducing the wire. expense; moreover, an automatic sub central station serving a small district may be made so compact that it requires but little space and no special building or room is required, but it" may be placed in a comparatively small box or inclosure on a pole or building.

Another object of the invention is to enable the subscriber to call central directly vby the usual operation of removing the receiver from the hook, and to enable central to call subscriber by automatic selection at the sub central station.

Another object of the invention is to r0- vide for sending over the trunk linesrom central the necessary calling impulses to select any subscribersline from the sub central station by the mere operation of the usual spring jack device at the central station switch board.

Another object of the invention in connection with a system indicating a plurality of trunk lines is to provide for. switching the subscribers line at the sub central station to a trunk line which is not in use.

tion with such a multiple trunk system is to provide for switching the calling device at central on to a trunk line which iSflnot in use.

i Ai1other object of the invention is to provide for using the same trunks for the incoming calls that are used for the outgoing calls, thereby reducing'the number of trunks necessary for a given number of subscribers lines.

minates at a sub central station from which calls are automatically tru'nked to the cenis manually connected to trunk leading to ers line terminates and where the trunk 'is automatically connected to said called subscribers line.

In the accompanying drawings: Figure l is a diagram of'the system. .Fig. 2 is a side elevation of a selecting switch which is provided both at the sub central station and at central station, being automatically operated at the sub central station by the subscribers line and constituting a line switch and being automatically operated at the central station by the jackand constituting a'jac switch.

of impulses. Fig. 5 is an end elevation of Fig. 4. Fig. 6 is a side elevation of a truni: switch for connectinga call at the sub central station to the trunk line.

central stations, showing the general arrangement.

Referring to Fig. 1, the central station is provided with a switch board, having for each subscriber a selector 1 and a jack switch 2. The usual jack, relay and signal devices are also ,provided at the central station and any desired number of trunk lines 4, 5 lead to the sub central stations, there being as many trunk lines for each sub central station as are warranted by the business thereat. Each sub central station is provided with a line switch 7 for each subscribers line and with a trunk switch 8 for each trunk line.

Fig. 3 is-a side elevation of 2. Fig. 4] is a side elevation of a selector for automatically sending to the line selective sequences Another object of the invention in connec In this system each subscribers circuit tertral station. At the central station the call sub central station at which called subscrib- Fig. 7 is an end elevation of Fig. 6. Fig. 8 is a diagram 1 I of a central station and a plurality of sub armature.

two sides of after set "or member 10. This magnet is in a local circuit controlled by the jack in the switch board ashereinafter described, and this circuit also includes a pair of contacts 20, 21 operated by the armature lever 15, and two other pairs of contacts 22, 23, 24, 25 operated by an arm 26, carrying a hook 27 to engage a hook 28 on the armature lever. The pair of contacts 22, 23, as well as the contacts 20, 21, are closed when the armature 18 fully retracted, and the pair of contacts 24,"

25 is closedby the hook means 28, 27 when the armature means starts to move forward, the contacts 22, 23 being broken at the same time, thus establishing a circuit for a magnet independent of the back contacts 20, A fixed pin 29 is provided to engage an incline 30 on the hook 27 when the armature is fully attracted, to raise said hook, releasing it from the hook 28, whereupon the member 26 springs back to normal position, opening this auxiliary circuit and putting the magnet again under control of the main contacts 20, 21, 22, 23, which are not closed until the armature is fully retracted. By this means a definite length of stroke is given to the The armature lever of magnet 14. is adjusted for such rapid operation by the magnet and the retractive springs thereof, that at each retraction the pawl 16 is moved back to engage withthe next tooth of rack 17 of member 10, before the said member 10 has time to move backappreciably under the influence of its spring 12. The inerti'a of member 10 is such as to preventit from moving back rapidly enough to mterfere with the operation as described.

The are member 10 is provided with a plurality of series of pro ections or pins 31,

' 32, the pins of series 31 operating on one of a pair of spring contacts 38, 34, and the pins of series 32-operat1ng on one of a pair of contacts 35, 36. One of the contacts, as 34,

" 36 of each pair has an inclined end portion to be engaged by the pin 81 or 32, to close the contact on the other one of the pair, when .the arc member 10 is beingoperated as above stated, the pair engaging on the other side of the flange when} the arc member is returning, so that the contacts are not closed in such return. These pairs of contacts are connected send impulses to the line on the e metallic circuit hereinthe number of pins in the res ective series determines the selection effecte at the other end of the line. Two pairs of contacts 37, 38 are closed by the pressure of member 10 when in fully operated position. A selective impulse transmitter such as above described, is provided for each suhscribers line, and the spring jack devices of the switch board are individually connected to the operating means for said transmitters, so that manual operation of the spring jack selects one of the impulse transmitters for operation. The line switch (description of which will also serve for the jack switch) comprises an arm 40 mounted to turn on an axis 41 and drawn by spring means 42 in a given dircction, its motion in that direction being arrested by a stop 43, said arm being operated in the other direction by a magnet or solenoid 44, whose core or armature 45 is connected to a strap 46 operating over a segment 39 connected to said arm. Said arm carries two pairs of contacts 1 .7, 48, (L9, 50, passing, in the operation of the arm, respectively over four rows of contacts 51, 52, '53, arrangcd'on an insulating plate 56 in concentric relation to the axis of motion of the arm i0. Said arm is also provided with a ratchet rack segment 58 to be engaged by a stop 59 on an armature 60 of a magnet 61.. This armature lever carries a contact 62, cooperating with a fixed contact 63, to control connections to the line switch as hereinafterset forth.

The trunk switch, see Figs. 6 and 7, comprises an arm 65,1nountcd to turn on an axis 66 and drawn by a spring 67 in a given direction, its motion in that direction being ar-1 rested by a lug .68 on the arm engaging a contact spring 69 which thus normally makes contact with a fixed contact sprin'g'70 and is held away from another fixed contact spring 71 Said arm 65 carries three con- .tact springs or brushes 73, 74, 75, adapted in the movement of the arm to pass :respectively over three segmental rows of contacts 77, 78, 79, arranged concentrically with the axis 66 and carried by an insulating plateSO. Said arm is operated step by step in this movement by a plurality of electromagnetic selecting devices, operating in sequence to move the arm, first by large steps, passing over several contacts at a time, and then by smaller steps, passing over one contact ata time. These two operations are 1 performed in sequence by two magnets 81, 88. The armature lever 82 of magnet 81 is retracted by a spring 83, and carries a pawl 84 to engage, in the attraction of the armature, a ratchet rack segment 85 on arm 65. The secondary step by step operating means comprises a magnet 88 whose armature lever 89 has a retracting spring 95 and a pawl 90 engaging a ratchet rack segment 91 on a Marrying a pawl 94 engaging the ratchet rack segment on the switch arm 05. A. retainingpawl 96 is provided for holding the rack 91 from back movement, this pawl being pressed toward the rack by a spring 97. Lever 92 operates, byan insulating lug 100, a contact spring 101 normally held back against a contact 102 and away from a contact 103, the said contacts controlling the operating circuit of the resetting means. The resetting means comprises a magnet 10.) whose armature lever 106 is retracted by a spring 107 and carries a pawl 108 which is drawn downwardly 'by a spring 109 and normally rests on a pin 110 extending from an arm 111 on the segment 85. so that a shoulder 112 at the outer end of said pawl is normally above a slide 113 mounted to move longitudinally on fixed pins 114, said slide having a shoulder 115 adapted to be engaged by the aforesaid shoulder 112 on the pawl when the said pawl is allowed to drop by movement of the segment 85 as hereinafter set'forth. The said slide 113 has pins 117, 118. 119 adapted to release the respective pawls 90, 94, 96 aforesaid when the slide moves back on release of armature of magnet 105. Pawl 84 is released from rack 85 by a fixed pin 120 acting on an.incline 121 on the pawl when the.latter is retracted. Armature 106 of magnet 105 presses contact spring 122 against a contact spring 123 when magnet 105 is energized. A connection 198 leads from the armature 184 for trunk line 4 through switch contacts 101, 102, and through the first operating magnet 81 of the trunk switch to ground, and an= other connection 199 leads from the armature 185 for the other side 5 of the trunk line through the second operating magnet 88 of the trunk switch toground, closure of said contacts being controlled by said magnet 88. The other contact, 103, whose connection is controlled by the said magnet 88 is connected by Wire 200 to relay 105, whence a connection 201 is made to the armature of relay 196, the back contacts of said relay being connected to ground. The wires 198, 199 connected to the armatures 184, 185 for the respetive'sides of the trunk line'5, 4, are connected by-wires 203, 204 to the respective contact brushes 74, 75 on the arm '65 of the trunk switch, the other contact brush 76 thereof being connected to ground by wire 205. The fixed contacts 77, 78, 79 of the trunk switch are connected by connections 206, 207, 208 to respective multiple .lines 210, 211, 212, which are multipled to corresponding contacts. in the different trunk switches, there being as many trunk switches as there are trunk lines,

The local operating circuit for the selecting impulse transmitter is from ground through battery 99, wire 125, and a circuit 126, including the contacts 20 to 25 of transmitter operating magnet 14,to brush 49 of the jack switch. Contacts 53, 54 of the jack switch at central. are connected by wires 127, 128 to wires 160, 161 which are multipled to similarly located contacts on all of the jack switches. \Vire 161 is connected to ground through magnets 130 and 129. A circuit leads from movablecontact 50 which coiiperates with the series of contacts 54 through the armature and front contact of stop magnet 61 of the jack switch to ground. This connection serves as a trial ground. i

The trunk line wires 4, 5 are connected to two armatures 139, 143 of a magnet 130, whose front contacts are connected by wires 144, 145 to the contacts 51, 52 of the jack switch. Movable contacts 47, 48 cotiperating with these fixed contacts 51, 52 are connected respectively to circuits 131, 1320f the'selecting impulse transmitter, the circuit 131 including contacts 33, 34, 37, and circuit 132 including contacts 35, 36, 38. Battery wire 125 is also connected by wire 157 to front contact of relay 124, the armature of said relay being connected by wire 164 to ma ets 44 and 61 of the jack switch.

The se ecting impulse transmitter is adapted to send impulses over the two sides, V1z., the sleeve and tip sides of the line, sequentially, contacts 33, 34 operated by the first series 31 of pins being connected 'through circuit 131 and contacts 37 to the jack sleeve 133 and the contacts 35, 36 operated by the second series of pins 32 being connected by circuit 132 and contacts 38 to the jack tip 134. Plug sleeve 135 is connected by wire 136 through a condenser 137 to the back contact of an armature 143 of the relay 130. Plug tip 138 is connected by wire 140 to condenser 141, whence a wire 142 leads to the back contact of another armature 139 of relay 130. A connection leads from battery wire 125 through wire 148, relay 149 and wire 150 to wire 136 leading to the plug sleeve 135. The circuit 152 for signal 151 leads from wire 148 to front contact and armature of relay 153, and back contact and armature of relay 155. Relay 153 is in a ground-connection from. wire 143. Relay 155 is in a ground connection from wire 140.

The subscribers apparatus, indicated in a general. way at 7, includes the usual re-- ceiver and transmitter, herein termed the instrument 165, bell 167, hook switch 168 and condenser 169, connections being made from the instrument,- and from the hook switch to the subscribers line 171, 172. Wire 171 is connected to contact brush 47 'on the arni 40 of the line switch and is connected by wire 173 to relay 174, the other terminal of which is connected to its own armature, and the front contact of the relay beingconnected by wire 175 through the operating solenoid or magnet 44.to

&

The battery 17? at the sub station is 0011- nested by wire 178 to the armature of relay 17 1 and to the brush 19 of the line switch. Fixed contacts 51, '52 of the line switch are connected respectively by wires 180,181 to two multiple lines 182, 183 which are connected respectively to two sides of a trunk line 4,

i 5. The sald two sides of the trunk line are connected respectively to back contacts of two armatures 184, 1 5 of a relay 186 in a circuit- 187, grounded at one end, and extending as a multiple line in the sub station. Each of fixed contacts 53 of the line switch is connected by a wire 188 through a relay 189 to ground, and each fixed contact 54: is connected by a wire 194 to a multiple line 191. The armature of relay 189 aforesaid is grounded and controls by its back contact battery current also flows through front closes springs 62, 63 grounding the magnet' 'a circuit 193 lending to the back contact of the trunk switch, contact 69 of said switch being connected by wire 194 to the multiple line 191 aforesaid. The front contact of rela 189 is connected through wire 195 and re ay 196 to contact 123, against which contact 122 is pressed by operation of trunk switch resetting magnet 105, said contact 122 bein connected by wire 19? to battery wire 118.

The operation is as follows:On the re ceiver" being removed from hook 168 of subscribers instrument, closing contacts of hook switch, current from battery '17? flows through relay 1'74to sleeve side 171 of sub; scribersjine to instrument, through instrument to tip side 172 of line and to ground through retardation coil 1%. This energizes relay 174: which, closing its contacts, causes current from battery 177, to pass through windings of solenoid 441 to ground. When brush 50 onarm 40 of line switch reaches a contact 5-1 which is grounded,

contact of relay 174, through magnet 61, end brush 50 to contact 54 which connects to ground throughwire 194:, contacts 69, 7 0, wire 193 and armature of relay189. The armature of magnet 61 on being attracted at 63, and locking the arm 40 with brushes 47, 48, 49 resting on contacts-51, 52, 53mm;- responding to contacts 54wit-h which 'con tact has been made. Brush 50 being in ad Vance of the others when the arm is locked, has passed over contact 54., and is on open circuit, Brush 49 on reaching contact 53 closes the circuit through wire 188 and reclose L 99 through wires 125, 164- as above traced,

lay 189 to ground, and current also flows through wire 18? to relay 186 to ground, opening contact at relay 189 and taking ground oil contact 51, and also opening the connections through armatures 184, 185 to the trunk line. Contact 5 1 being nmltipled through a group of line switches, the ground is opened to prevent other switches from engaging on it while in use. The subscribers line is now connected through brushes 47, 18, contacts 51, '52 and wires 180, 181, 182', 183, to trunk leading to central station, and relay 153 at central station is energized by current fr 'r battery 177, passing to tip side 5 of trunk and through armature 1413 and rela 153 to ground, relay 153 then closing circuit 152 and lighting lamp 151 on main switch board.

The operator at the central station after ascertaining the number that calling subscriber desires, inserts plug in jack correspondin g to that number, whereupon current from batter 99 passes through wire 14:8, relay 1 19 am wires 150, 137, to the sleeve of plug and jack and to ground through relay 124:, which closes connection from battery wire 125 for energizing solenoid 41 of jack switch, the current then passinglfrom wire 125 through wire 157, armature of relay 124- and wire 16% to the solenoid 1 1, and the solenoid being energized, the aclt switch solects a trunk, not already engaged, to a subcentral stat-ion,in the following manner: As the long contact 50 of the jack switch passes onto any contact 51 it will, it the trunk corresponding thereto be not busy, circuit as follows: from battery thence through magnet 61 and wire 162 to contacts 50, 51; and wires 12?, 1.60, 166, through contact of relay 153, wire 15 0 and back contact of relay 129 to ground; iuagnet 61 being thereby energized o )crates its armature to stop the motion 01: the jack switch,.the cont-act- 50 meanwhile moving oil the contact 54, and contacts 1-7, 48, -19, coming onto the corrcspomlingset of co11- tacts 51, 52, As contact 50 leaves con tact 54, the ground connection just traced is broken, but before this talges place magnet 61 has closed a ground for itself at ($0 therebymaintaining the jack switch in operative position. Closure of contact -19 onto contact 53 establishes a circuit from wire 125 through contacts 22-, 23, 20, 21 bywire 126 to magnet 14, contacts 419, 53, wires 128, 161 and relay 129 to ground. Relay 129 then breaks the initial ground for contact 54 corresponding to this trunk in this and all other jack switches multiplcd thereto.

thus preventing any subsequent connection being made on this trunk as long as it is in use, and at the same time relay 1R0 operates armature 139, 143, to take both sides of the selected trunk atc'entral, ofi' oi ground and sleeve sides of the trunk.

put them on the connections 144, 145 of the jack switch, thus establishing a calling connection to the unused trunk, which it will be understood is a dilierent trunk -from-the one over which central Was called.

The energization of magnet 14 acts through its armaturew 15 and hooks 28, 27, to causcront-act 24 to make with 25 before contact 20 breaks with contact 21, thus maintaining the circuit to magnet 14 until the further armature stroke is completed, whereupon the hook 27 (see Fig. 4) is dis engaged from hook 28 by incline 30.riding on pin 29, allowing the spring contacts 24, 25 to separate. Both circuits for magnet :14 are now broken and the armature is'retracted and closes at 20, 21, the original circuit for the magnet, whereupon the opera tlon is repeated and the magnet 14 is thus intermittently operated throughout-its full stroke. i

In the above described position of the jack switch, the contacts 47, 48 rest on con tacts 51, 52,and complete the connections from the two sets of contacts of the selective impulse transmitter to the tip and These'circuits are traced as tollowsz-on the sleeve side, from wire 125 by contacts 33, 34 and wire 131 to contacts 47, 51, wire 144, armature 139, sleeve side 4 of trunk, armature 184, wire 198, contacts 101, 103,. and magnet 81 to ground and back to battery 99. On the tip side, from wire 125, by contacts 35, 36, wire 132, contacts 48, 52, wire 145, armature 143, tip side 5 of trunk, armature 185, and wire 199 to magnet 88, and ground.

By operation of the selected impulse transmitter, sequential series of selective impulses arethus sent out, first on the sleeve and then on the tip side of the trunk, the number of impulses at each side depending on the line number, (tor example, for star-- tion on 44 there would be 4 impulses on the sleeve and 4 on the tip). 'The firstseries of impulses operates through magnet 81 to move the trunk switch arm forward stop by step, each step coverii'ig a group of the contacts of the switch, and the second series of impulses moves the arm 65 by smaller steps, each step advancing it from any row of contacts to the next, in the group to which it has been brought by. the first operation When the trunk switch has thus been brought to proper position the connec-' tions are established from side 4 of the trunk through wires 198, 203, contacts 7 5, 78 and wires 207, 211, to one side of subscribers line, and from side 5 of trunk by wires 199, 204, contacts 74, 77, and wires 20.6, 210 to the, other side of subscribers line, thus putting the subscriber onto the trunk for communication. At he same time the brush 76 passingonto contacts 79, in the same radial row, establishes a connection to ground for the stop magnet of the corresponding line switch at-the sub central station, so that when the subscriber takes his telephone from the hook in response to a callfrom central station the circuit is closed through said stop magnet from battery 177 through armature of relay 174 and the said stop magnet 61 holds the line switch from operation. As the selective impulse transmitter completes its motion, it closes contacts at 37. 38, for the tip and sleeve connections of the jack, independent of the contacts 33, etc.,'so that the plug which is connected through wires 136, 140, and condensers 141, to the trunk to calling subscriber, the connection is continued through the plug and contacts 37, 38, to trunk to called subscriber.

When the. magnet 88 has been operated as above described, it closes contacts 101, 102. so that the current flowing from the sleeve side of the cord tothe trunk passes through wire 198, contacts 101, 102 wire 200, through magnet 105, wire 201, and back contact of relay 196 to ground, thus energizing magnet 105, and attracting the armature 106 thereof (see Fig. 6) so that when the operator at central withdraws .the plug from the jack and this circuit is broken the retraction of the said armature operates through members 108, 113, to release the detaining pawls 90,

94, 96,'and allow the trunk switch to be set to normal position by its spring 67. As

trunk switch is thus reset arm 111 releases the member 108 from member 113, thus re-. storing the original condition by allowing pawls 90, 94, 96 to move under the actionof spring 97, or of gravity, to position to engage the respective rack means. The term subcentral station is herein applied and limited to a branch central station at a distance from the central station in distinction to switching devices at the central station, so that the length of the trunk lines connecting them is an importantconsideration in the cost of the system, and the saving ofwires by having comparatively short subscribers wires converge to the proximate sub central station instead of to the main central station, efiects a material reduction in cost. This advantage is secured in maximum degree by the use of the automatic switch at such sub central station as this enables the distribution of the subscribers lines in small shortest possible lines. T- is feature of the sub central stations, in connection with the application of the automatic switch, is essential to tlie invention and as. far as'I am aware is original with me.

The local circuit of a subscriber is from battery 177 through wires 178, 179, relay 174., wire 171, subscribers instrument 165, wire 172, retardation coil 166, to ground. The operation of the subscribers instrument in the circuit as traced, sets up impulses roups giving the ture 185, trunk through the trunk to central in the incoming talking circuit as follows :--from wire 171 through brush47, contact 51, wires 180, 182, trunk 5, to central, armature 143,-condenser 137, wire .136, sleeve 135 of cord, tip 138 of plug, Wll '6:l4:0, condenser 141, armature 139, and from central by trunk 4, wires 183, 181, contact 52, brush 48, to wire 172. When the connection has been established from central to the called subscriber the talking circuit to the called subscriber is from wire 136, sleeve 135 of lug, sleeve 133 of jack,

wire 131, throughcircuit closer 37, to brush v47, contact 51, wire wires 207,211, (and the hook 168 being up) :subscribers instrument 165, wires 210, 206,

contact 77, brush 74, wires 204, 199, arma- 5 back to central station, armature143, wire 145, contact 52, brush 48, 'circuit 132, through circuit closer. 38 to the tip 134 of jack and tip 138 of plug, wire 140, through relay 155, to ground. Current is fed for the talking circuit from battery 99, wire 148, relay 149, wire 150, to wire 136 aforesaid, whence the circuit extends to the subscriber as stated, and returns through ground 166 and relay 155. When connection has been made by the switch board spring and outgoing talking circuits. are connected through the spring jack devices, the insertion of the plug into theselccted jack first 5. automatic operation above described and thereupon establishing the talking circuit to said subscriber through the same spring jack, and. the complete talking circuit is through the two circuits as above described, 0 said circuit joining at the wires, 136, 140, it being understood that the outgoing talking circuit is'to a' different subscriber from that of the incoming talking circuit. Ringing current is cut in on the cord circuit 136,140, 5 by usual means, not shown, the current passing as above traced for the circuit, except that on reaching subscribers station it passes through the bell 157 by reason or" the hook being down. If the line is busy on receiving a call, relay 189 is en ergized and current passes from battery 177 through wires 178, 197, circuit closer 122,

123, relay 196, to ground at relay 189. Re-

i ly 196 on being energized opens ground on 5 wire 201, thus deenergizing relay 1G5, and

14-4. to trunk 4-, arma-' 5 ture 184, wires 198, 203, brush 75, contact jack devices at central, the incomin causing the selection of a subscriber, by the outgoing talking central station having automatic switch means responsive to selective impulses from the central station to connect one end of the subscribers line to a line from the central station, a plurality of selective impulse transmitters at the central station, each solective transmitter being adapted to send a selective series of impulses corresponding to one of the subscribers lines at the sub central station, and manual switch means at the central station having an individual connection for each of the selective impulse transmitters, whereby the said manual switch means manually selects the selective impulse transmitter, and saidv transmitter automatically selects the subscribers line.

2. A telephone system comprising a central station, a plurality of sub central stacentral station to each sub central station,

and a plurality of subscribers lines extend ing from each sub central station, an automatic switch in each sub central station, for each subscriber-s line, for automatically connecting a subscribers line to a trunk line which is not in use; a manual switch at the central station having an individual connection for each subscribers line at the sub central station, and means controlled by such individual connection for sending selective impulses over a trunk line.

A telephone system comprising a central station, a plurality of sub central stations, a. plurality of trunk lines from the central station to each sub central station, a plurality of subscribers lines extending from the sub central station, an automatic switch in each sub central station, for con meeting the subscribers lines to a trunk line which is not in use, a plurality of trunk switches in each sub central station, responsive to the impulses from the trunk lines to automatically connect any trunk line to any of the subscribers lines, a manual switch at the central station having individual connecting means for each subscribers line at the sub central station, and means controlled by such individual connecting means for sending selectedimpulses over the trunk line.

4. A telephone system comprising a central station, a sub central station, a plurality of trunk lines from the central to the sub central station, a switch-board a pparatus at the central station comprising spring-jacks and plugs, a selective impulse transmitter at the central station for each subsci'ibcrs line at the sub central station to send selective impulses over a trunk line for the selection of subscribers line, means controlled by the operation of the spring-jack and plug to operate said selective impulse transmitter and an automatic. switch at the sub central station controlled by the selective impulses to connect the operating trunk line to any subscribers line at the sub central station.

3O rality of transmitters for sending selective for each subscribers line for sending over 5. A telephone system comprisinga central station, a sub central station, a plurality of trunk lines connecting the central'station and sub central station, means for grounding each trunk line at the central and at the sub central stations, automatic switches at the central and sub central stations for connecting the operating circuits at each station 1 to a trunk line which is grounded at the other station, and means controlled by the operation of the automatic switch at eachstation to break the ground for the trunk line at that station. I,

6. A telephone system comprising a central station, a sub central station, trunk lines connecting said stations, and adapted to form a metallic circuit, a plurality 'of selective impulse transmitters at the central station, a switch board comprising springjack devices having individual connections for manually selecting selective impulse transmitters, connections, whereby said selective impulse transmitters are connected to send impulses over-the line, and a talking circuit connection through the same spring jacks of the switch boardthat control the selected impulse transmitters.

7. In a telephone system, the combination with a switch board-comprising spring jack devices, of a plurality of trunk lines, a pluline impulses, operating means for said transmitters controlled by the spring jacks, an automatic. switch for selectinga trunk line, and talking circuit connections to said trunk lines controlled by the said spring jacks, and by saidautomatic switch.

8. Ina telephone system the combination with the. spring-jack devices of a switch board, of transmitters for sending selective line impulses and each comprising means operating automatically to transmit a defi nite sequence of impulses, operating means for said transmitter controlled by the springjacks, and a talking circuit connection, through the same spring-jacks that control the operation of the selective impulse trans-' mitters.

9. In a telephone system, a trunk line, subscribers lines, a selective impulse transmitter the trunk line selective impulses corresponding to the subscribers line, an automatic operating means therefor, and selective 1mpulse transmitter controlling means for bringing any one of said transmitters into operation on the trunk line.

10. A telephone system, a trunk line, subscribers lines, a selective impulse transmitter for each subscribers line for sending over the trunk line selective impulses corre sponding to the 'subscribers line, an automatic operating means therefor, selective impulse transmitter controlling means for bringing any one of said impulse transmitters on the trunk line, said controlling means comprising 'sprin jacks and circuits operatedthereby, an magnets in said circuits for operating the selective impulse trans mitters.

. 11. A telephone systemcomprising a central station, a sub central station, a trunk line from the central to the sub central station, a plurality of subsc'ribers lines from the sub central station, a plurality of selective impulse transmitters at the central star tion, each transmitter comprising means for automatically transmitting a definite sequence of impulses, a manual switch board and circuits therefor controlling the operationof the respective selective impulse transmitters.

12. In a telephone system, atrunk line, a sub central station connected thereto, a plurality of subscribers lines-connected to the sub central station, a trunk switch havingan operative connection with the trunk line to be operated by selective impulses therefronu said trunk switch comprising contacts and circuits therefor for connection with any. one of the subscribers lines, the contacts of said trunk switch being arranged in groups and said trunk switch being provided with two operating means, one of which steps the switch forward from group to group, and the other steps the-trunk switch forward in each group, the said two operating means being connected for operation from the two sides of the trunk line, and a central station provided with a transmitter for sending se- 'quential series of impulses over the two sides of the. trunk line.

In testimony whereof, I have hereunto set my hand at Los An'ge'les- California this 20th I day of April 1907.

CHARLES R. AUSTIN. 

